A. Field of the Invention
This invention relates to a process for manufacturing a transparent, conductive film. In more detail, the invention relates to a process for manufacturing a high-quality transparent, conductive film at high speed using the ion-plating method
B. Description of the Prior Art
Conductive film consisting of plastic, etc. is used in various fields such as for antistatic materials, electromagnetic wave shields, touch panels and display units. A process for manufacturing a conductive film by depositing a thin film of a conductive material such as a metal and metal oxide on the surface of a film made from plastics, as well as a process for providing an organic polymer itself with conductivity are generally well-known.
The process of providing an organic polymer film with conductivity is, however, now in the fundamentally investigative stage. There are many unsolved problems remaining in the process of depositing a thin film of a conductive material, though commercialization is expected.
Methods have been proposed for depositing thin films such that the thin film is deposited on the surface of plastic film moving from a delivery roll to a wind-up roll by methods such as metalizing, sputtering and hollow cathode ion-plating. These methods, however, have serious problems such as poor productivity due to the low depositing reactivity of the thin films, the inevitable adhesion of dirt to the manufacturing equipment including the cathode, low thermal stability and unavoidable heat build-up in the plastic substrate. Therefore, thin conductive films with good conductivity, high adhesiveness to the substrate, good durability and uniform quality have not been effectively manufactured.
Meanwhile, an ion-plating method using a pressure-gradient discharge plasma gun has also been proposed (see the Japanese publication entitled Vacuum, Vol. 27, No. 2, Pg. 64, 1984). According to this method, a pressure-gradient discharge is conducted such that an intermediate electrode is located between the anode and the cathode, while maintaining pressures at the anode and cathode regions at approximately 1 Torr and 10.sup.-3 Torr, respectively.
Such ion-plating method is used for dry-coating on the surface of the material to be treated so that the plasma flow is emitted horizontally from the plasma source and turned perpendicularly right above the source material crucible, which is placed facing upward so that the plasma converges to ionize the raw material for the thin film.
The method has many advantages such as non-adhesion of the dirt on the plasma gun, a high reaction rate, uniformity, and high adhesion of the thin film to the substrate.
Ion-plating by gradient discharge has never been adequately investigated in terms of applied technology and in respect to the development of a practical apparatus. Especially, the application of ion-plating to the manufacture of transparent conductive film at high speed, and the selection of the operational conditions and process, as well as the dry-coating of moving articles of a film material have not yet been developed.
Such a film having high transparency, (which high transparency is indispensible for practical use as a functional film), has not yet been manufactured.
This invention aims to provide an effective process free from those problems involved in manufacturing a high-quality, transparent, conductive film. In more detail, the invention provides a process for manufacturing a transparent, conductive film at high speed according to the ion-plating method and winding the film on a wind-up roll.